The present invention is a method of transplanting a container grown plant which minimizes physical and biological distrubance to the plant. The method is particularly well adapted for transplanting plants grown side by side in grid-like trays.
Many plants are started from seeds or cuttings in glass houses or similar controlled environment conditions. It is often the case that these plants must be transplanted to larger containers as they grow in size. Normally this is done by pushing or lifting the plant out of the original container with the expectation that the root structure will bind the original growing medium into an intact plug. Starter rooting media are generally very porous and often the root structure is not sufficient to maintain the integrity of the medium when it is removed from the original container. This results in the growing medium falling away from the roots so that there is considerable disturbance to the roots and trauma to the plant and often major transplant loss. The plants can suffer a considerable set back and there may be a significant increase in the time required to grow the plant to the desired size. This problem is particularly severe with cuttings that ordinarily have not developed a vigorous root structure by the time of a first transplant. It can also give a false appearance of poor quality if the rooted cuttings are sold directly into the consumer market.
One method which was developed for overcoming friability of the growth medium is described by Finch in British Patent 1,399,822. This inventor describes a potting substrate containing at least two substances which subsequently form an alginate gel by base exchange. The inventor notes that this ensures adequate air and moisture passage and heat exchange within the growth medium. He also notes that it can facilitate removal of the plant and soil mix from a container. The inventor draws an analogy that after gelation and hardening of the alginate the soil particles are cemented together "like bricks . . . in a wall."
A calcium alginate gel is preferred in the Finch process. The gel is created in situ by the inclusion of a soluble alginate in conjunction with a relatively low solubility calcium salt such as calcium citrate or sulphate. While the invention appears to be primarily directed to the formation of pelleted seeds, it can also be used to aid repotting with the use of automatic machinery. It is important to note that the soil is treated initially; i.e., when the seed is planted or before a cutting to be rooted is inserted into the mixture. The gel then forms over some period of time due to the poor solubility of the calcium salt.
The present inventors have found that there are significant disadvantages inherent in initially treating a potting soil mixture with a binder of the type described by Finch. As the seed germinates and roots begin to develop, or as roots begin to form on the cutting, it is desirable for the growth medium to be very loose and porous. It is necessary for the tender young roots to force their way through the soil mixture with the inevitable displacement of some of the soil particles. The soil mixture at this time must have good porosity to prevent waterlogging and provide good aeration. If the soil particles are tightly bonded, this early root growth can be significantly inhibited. There is a second problem as well. Most organic binders are subject to rapid decomposition due to the action of soil microflora. Thus, a medium which was initially sufficiently bonded to enable handling will often have degenerated into a mass of completely loose particles by transplant time. This is especially true when the growing period exceeds three or four weeks.
As will now be described, the present invention satisfactorily overcomes the above-noted deficiencies.